The construction and landscaping trades often require the installation of soil retaining walls for temporary excavation support, as permanent subsurface walls, and as permanent above-ground retaining walls. Such soil support walls are conventionally constructed from elongate beams, referred to as lagging, that are stacked in horizontal disposition to form a vertical or inclined wall. The stacked beams are often supported by vertical soldier piles. Tie-back anchors may also be utilized to support the stacked beams, whereby deadman elements are buried in the soil behind the wall and tied to the wall by an elongate cable or rod.
Lagging members for soil support walls are typically either timbers or are formed from reinforced concrete. In the case of wooden timbers, the lagging is heavy and labor intensive to install. The configuration of the beams is limited, and any passages within the beams for the placement of drains, reinforcing members, or electrical wiring must be formed by cutting or drilling, which is also labor intensive and therefore expensive. Such cutting reduces the structural integrity and therefore is typically avoided. Additionally, the shape of the timbers is essentially limited to rectangular planks or cylinders, given the nature of the material.
In the case of preformed concrete lagging, the lagging members are also very heavy and therefore require labor and machinery intensive placement. Although a wide variety of shapes and configurations of lagging can be precast, once cast it is difficult to adapt, requiring abrasive cutting and drilling. Alternately, concrete lagging can be cast in place, but the requirement for the provision and placement of forms is also labor intensive and costly.
Construction of temporary excavation support walls often occurs under adverse conditions, with loose soil and mud being present. The weight of conventional timbers or concrete lagging all too often results in slippage and injury of construction workers, particularly under such adverse conditions.